Diagnosis: body robust, deepest behind head, then tapering evenly; nape rising moderately steeply in adults, bill long, flattened and sword-like; no teeth in jaws in adults. 2 dorsal fins, both short, the first with 21-30 finrays, the second with 3 (the fins joined in juveniles and young); similarly 2 anal fins, the first with 12-13 finrays, the second with 3 (also joined in juveniles and young); pelvic fins absent; caudal finlunate in adults, emarginate to forked in young; a large horizontal keel on each side of caudal peduncle. No scales in adult, but peculiar scale-like structures present in young, gradually disappearing. Vertebrae 26. Colour: back and upper flanks uniformly dark brown, sometimes with a metallic blue tinge on back, lower flanks and belly light brown. Size: to 4.5 m TL, usually 2.5-3.5 m; specimens weighing over 650 kg have been reported.

Habitat: tropical and temperate waters, down to 800 m, strongly migratory, solitary for the most part, but occasionally in concentrations; aggressive. Food: a wide range of fishes, with herrings, mackerels and carangids preferred, also squids; the sword-like bill is believed to be used to slash into shoals, as well as in defence. Reproduction: January-October in eastern Atlantic (a peak in February-April in western Atlantic), June-September (with a peak from the end of June to August) in Mediterranean, juvenile stages have jawteeth, a form of scales, and single and long dorsal and anal fins; spawning is in the warmer parts of the range, with migrations to the cooler waters for feeding.

Distribution: warm and temperate parts of area, but straying as far northward as Iceland in summer months; throughout Mediterranean, also Black Sea. Elsewhere, worldwide in tropical and temperate seas.